A hammer drill apparatus can comprise a drill chuck mounted on a drill spindle having an axial passage, through which the hammer stroke is transmitted by an impactor or ram through the hollow drill spindle, to the end of a drill bit held by an array of clamp jaws of the drill chuck.
Means are provided for coupling of the drill chuck to the drill spindle, while preventing drill chuck rotation relative to the drill spindle, which also permit an axial play of the drill chuck on the drill spindle, unless the axial play of the drill chuck on the drill spindle is prevented by adjustment of the shift member on the drill chuck.
In my German patent application No. P 34 13 581.2 and the corresponding U.S. application Ser. No. 720,259 an improved hammer drill apparatus of this kind is described.
The coupling members effecting the keying of chuck to spindle are axial pins, which are engaged in cavities in both the drill spindle and the chuck body of the drill chuck. The cavities have a greater extent in the chuck body than the size of the pins and allow of course the desired axial play of the drill chuck on the drill spindle, while preventing rotary slip of the drill chuck on the drill spindle.
In this device the shifting member or piece is a coupling sleeve guided rotatably, but axially unshiftable, on the chuck body and about the drill spindle. This coupling sleeve is positioned axially adjacent a circular shoulder of the drill spindle and carries projections directed against that circular shoulder, which prevent axial motion free play of the drill chuck on the drill spindle by pressing on the circular surface of the circular shoulder of the drill spindle. However on the circular surface of that circular shoulder indentations are provided, in which the projections fit in at least to a depth equal to the displacement of the drill chuck during the axial play.
The coupling sleeve is rotatable so that the projections come into coincidence with indentations and can enter the indentations. Thus this arrangement provides the desired axial free play of the drill chuck on the drill spindle. However the axially directed force of the drilling is transmitted by the coupling sleeve in this apparatus since it is supported on a circular shoulder of the chuck body and also presses directly against the circular shoulder of the drill spindle, when the shift member is rotated to permit axial play. For transmission of the drilling force the coupling sleeve and its support on the chuck body must be constructed so as to be sufficiently stable.